1. Field of the Invention
The present invention relates to image processing apparatuses such as digital copiers which are provided with the capability of carrying out variable magnification of image data.
2. Description of the Related Art
Among the image processing capabilities implemented in digital copiers, which represent one type of conventional image processing apparatus, is the capability of carrying out variable magnification. This variable-magnification capability is such that processing is carried out independently in the scan and cross-scan directions.
FIG. 11 is a block diagram showing the sequence of operations during variable-magnification processing in the scan direction. At multivalue image processing section 402 of main image processing circuit board 400 in FIG. 2, to be described below, image data input from CCD circuit board 300 is acquired by enlarging first-in-first-out-type line memory(“first-in-first-out” is hereinafter referred to as “FIFO”) 71, and enlargement of the acquired image data is carried out at variable magnification unit 72, during which image data may simply be duplicated, or interpolative processing wherein new pixel data is created from pixel data at two adjacent points may be carried out, or the like. Furthermore, reduction of acquired image data is carried out at variable magnification unit 72, during which image data may be read intermittently, skipping of data occurring in units of pixels, or interpolative processing wherein new pixel data is created from pixel data at two adjacent points may be carried out, or the like, with the acquired image data being written to reducing FIFO line memory 73. Moreover, image data on which enlargement or reduction has been carried out is output to LSU 46 and printing on recording media is carried out.
FIG. 12A is a block diagram showing the sequence of operations during variable-magnification processing in the cross-scan direction. By varying the speeds of travel of first scanning unit 40a and second scanning unit 40b, which comprise reflecting mirrors 42a through 42c of digital copier 30 at FIG. 1, to be described below, the number of lines of image data input to photoelectric conversion element (hereinafter referred to as “CCD”) 44 is increased or decreased, variable-magnification processing being carried out on image data as a result of alteration in the number of lines in the original input at multivalue image processing section 402 of FIG. 2, and the image data which has been subjected to variable-magnification processing is output to laser write unit (hereinafter referred to as “LSU”) 46, and printing is carried out on recording media. If, for example as shown in FIG. 12B, control is carried out such that image data is sent to multivalue image processing section 402 with the same line having been acquired twice, an image of magnification 2× will be obtained. If, on the other hand as shown at FIG. 12C, acquisition with respect to a plurality of lines occurs once every other line, an image of magnification ½× will be obtained.
However, in the foregoing conventional processing, when variable-magnification processing is carried out in the scan direction, processing of image data has been carried out in the following order:
image data input→enlarging FIFO line memory 71→variable magnification unit 72→reducing FIFO line memory 73→image data output.
There has been separate control of write signals and read signals with respect to respective FIFO line memories. For this reason, two FIFO line memories—an enlarging FIFO line memory 71 and a reducing FIFO line memory 73—have been necessary. Furthermore, to vary speed of travel of the scanning unit that captures image data in the cross-scan direction in accordance with magnification ratio, a motor capable of carrying out variable speed control has been necessary and the task of writing a control program for control of speed in accordance with that magnification ratio has been tedious.